WEBVTT MARK TAUSCHECK FOUNDTHE PROBLENEAR STANHOPE.>> THIS IS WHAT EXPERTS THINK ACOMMON CHEMICAL USED BY FARMERSDOES TO OAK LEAVES.DEFORPING THEM AND -- DEFORMINGTHEM AND LEAVING THEM LOOKINGLIKE THEY'VE BEEN RAVAGED BYINSECTS.>> THAT WOULD BE THE ONE.>> THAT IS NOT A BUG.>> THAT'S SERIOUSLY TATTERED,DUE TO CHEMICAL.REPORTER: DAVE HAS A BEAUTIFULACREAGE IN HAMILTON COUNTY,SURROUNDED BY THE CROP THAT IOWAHAS BECOME SYNONYMOUS WITH.FOR DECADES, MANY CORN FARMERSHAVE USED A HERBICIDE WITH ASPECIFICALLY CHEMICAL TO CONTROLWEEDS.>> SEVERAL FARMERS ARE USING ITOBVIOUSLY.SO IT'S IN THE ATMOSPHERE.WHEN IT RAINS, IT COMES DOWN.REPORTER: WHEN IT LANDS ON OAKLEAVES, ESPECIALLY ON WHITESJUST STARTING TO OPEN UP IN THESPRING, IT'S BELIEVED THECHEMICAL CAN USE A CONDITIONKNOWN AS OAK TATTERS THAT STARTSWITH A DISCOLORATION OF THEYOUNG LEAF.>> IF YOU WAIT ABOUT SEVEN DAYS,THAT TISSUE FALLS OFF ON THEEDGE OF A LEAF.AND ALL YOU ARE REALLY LEFT WITHIS THE VEINS.>> IT'S HARD TO FIND A LEAFTHAT'S NOT AFFECTED.REPORTER: THE CONDITION ITSELFDOESN'T KILL THE TREE BUT CANWEAKEN IT AND MAKE IT MORESUSCEPTIBLE TO DISEASE.SEEING AFFECTED LEAVES NEXT TOHEALTHY LEAVES IS STARTLING.>> SO THIS IS OAK TATTERS.AND THIS IS A MATURE OAK THATHAS SOME SYMPTOMS BUT -->> BUT NOTHING LIKE THIS.>> NOT QUITE AS BAD.REPORTER: OAK TATTERS HAS BEENDISCOVERED EACH YEAR IN IOWASINCE IT WAS FIRST IDENTIFIED INTHE EARLY 90'S.THE D.N.R. DISTRICT FORESTERTOLD ME IF MORE RESEARCHVERIFIES HERBICIDE IS THE CAUSE,CHANGES SHOULD BE MADE.>> I HOPE WE DON'T THINK IT'SJU BUSINESS, BECAUSE WHITEOAKS AND OAKS IN GENERAL ARE KEYTO IOWA'S FOREST RESOURCE.

Experts at Iowa State University and the Iowa Department of Natural Resources believe a common chemical used by corn farmers is sickening oak leaves, leaving them deformed as if they've been eaten by insects.

The condition is known as oak tatters.

“That is not a bug; it's seriously tattered due to chemical,” said Dave Volkers, of Stratford, who owns a beautiful acreage in Hamilton County that includes timber and a pond. His land is surrounded by corn, and for decades, many farmers have used an herbicide called acetochlor with a specific chemical to control weeds and invasive plants.

“Several farmers are using it, so when it's in the atmosphere, when it rains it comes down,” Volkers said.

When it lands on oak leaves, especially on white and burr oaks that are just starting to open up in the spring, it's believed the chemical can cause a condition known as oak tatters, which starts with a discoloration of the young leaf.

"If you wait about seven days, that tissue falls off on the edge of the leaf, and all you're really left with is the veins,” said Mark Vitosh, district forester with the Iowa Department of Natural Resources.

“It’s hard to find a leaf that's not affected,” Volkers said.

The condition itself doesn't kill the tree, but it can weaken the plant and make it more susceptible to insects and disease. Seeing affected leaves next to healthy leaves is startling.

“So this is oak tatters, and this is a mature oak that has some symptoms but not quite as bad,” Volkers said.

Oak tatters has been discovered each year in Iowa since it was first identified in the early 1990s. The DNR district forester told KCCI if more research can verify herbicide is the cause, changes can be made.

“I hope we don't just think it's business because white oaks and oaks in general are key to Iowa’s forest resource," Vitosh said.

So far, the DNR has received more than 1,000 reports of oak tatters this spring -- most of which are from the eastern half of the state where white oaks are most prevalent.